Capabilities of Laser Ablation Mass Spectrometry in the Differentiation of Natural and Artificial Opal Gemstones

The potentialities of laser ablation coupled to ion cyclotron resonance Fourier transform mass spectrometry are evaluated to distinguish natural and artificial opals. The detection of specific species in both ion detection modes leads us to obtain relevant criteria of differentiation. In positive ions, species including hafnium and large amounts of zirconium atoms are found to be specific for artificial opal. In contrast, aluminum, titanium, iron, and rubidium are systematically detected in the study of natural opals. Moreover, some ions allow us to distinguish between natural opal from Australia and from Mexico. Australian gemstone includes specifically strontium, cesium, and barium. Moreover, it is also found that the yield of (H20)o-1(Si02)NX- (X- = 0-, OH-, KO-, Na0-, Si02-, AIO1-2-, Fe02-, Zr02-, and ZrO3-) and (Al20s)(Si02)nA102 ions depends on the composition of the sample when opals are laser ablated. Ions, which include zirconium oxide species, are characteristics of artificial gem. In contrast, natural opals lead us, after laser ablation, to the production of ions including H20, Al2Os motifs and AlO-, KO-, Na0-, and Fe02- species.